57 
in Portugal and Spain during the past century ; bogus gold dust 
made of platinum graius plated with gold. 
GOLD. 
Case 1. — Type specimens showing modes of occurrence of 
gold in nature. These are — crystalized gold ; free gold in the vein- 
stuff; ironpyrite containing gold disseminated through its sub- 
stance in invisible particles ; gold in slate (the gold in the speci- 
men is invisible) ; combined with tellurium in sylvanite, petzite, 
etc., {telluride ores) ; placer gravels in which the gold occurs 
as particles scattered through gravel and sands. A more exten- 
sive exhibit of placer gold may be found in Hall 32. 
Remainder of Case 1. — Gold ores, Pacific Coast. These are 
chiefly quartz, or quartz and pyrite. They are distinguished in 
general from ores of this class of other localities by a cleaner ap- 
pearance, the absence of rust and disintegration, and by the 
smaller proportion of pyrite present. 
Cases 2, 3, Rear. — Gold ores, Colorado. The ores of Cripple 
Creek, Col., which occupy the front of Case 2, should receive 
especial attention on account of their remarkable richness. Gold, 
which almost universally occurs free, is in these ores combined 
with tellurium (a substance related to sulphur) in the form of 
telluride ore. 
Case 3, Front. — Gold ores, New Mexico and Arizona. The 
gold of New Mexico occurs chiefly associated with large quantities 
of silver and lead. These ores, worked chiefly for the latter 
metals, may be found in another part of the hall. The ores in 
this case are those in which gold is the principal metal sought. 
Case 4, Front. — Gold ores. Black Hills, South Dakota. The 
Homestake ores included here are a good example of a low grade 
ore which may be made to yield a profit by working upon a large 
scale owing to favorable composition. Compare with the Alaska 
Treadwell ores in the rear of Case i, which are also low grade 
ores. 
Case 4, Rear. — Gold ores, Mexico. 
Case 5, Front. — Gold ores, Brazil. These are chiefly from 
the state of Minas Geraes. They are very varied. 
Cases 5, Rear, 6 and 7, Rear. — Gold ores. United States 
